1. Field of the Invention
The present invention relates to an alignment method for aligning a photomask with an object to be exposed with uniform patterns arranged in a matrix and conveyed in a direction, and more specifically to an alignment method, an alignment apparatus, and an exposure apparatus capable of performing highly accurate alignment for a pattern having a complex shape.
2. Description of Related Art
In this type of conventional alignment method, an imaging device, which has a plurality of light receiving elements arranged in a straight line in a direction orthogonal to a conveying direction of a color filter substrate, captures an image of a plurality of rectangular pixels formed on a color filter substrate (an object to be exposed), detect the position of a left-side edge portion of a left-end pixel on the color filter substrate on the basis of brightness information of the captured image, calculate the amount of position displacement between the position of the left-side edge of the left-end pixel and the reference position (target position) preset in the imaging device, and move a photomask in the direction orthogonal to the conveying direction of the color filter substrate so as to correct the amount of the position displacement to thereby perform an alignment between the photomask and the color filter substrate (for example, refer to Japanese Laid-Open Patent Publication No. 2008-76709).
In the conventional alignment method, however, the position at which the brightness changes from dark to light is detected to perform the alignment between the patterns of the object to be exposed and openings of the photomask with reference to the positions. Therefore, for a pattern having a simple rectangular shape, it is easy to detect a reference position set on the edge of the pattern and further to perform the alignment. However, for a pattern having a complex shape such as a wiring pattern within a pixel such as, for example, a TFT substrate or a pattern having a complex outline shape obtained by epi-illumination, it is difficult to detect a reference position set on the edge portion of the pattern and further to perform the alignment. Accordingly, it is difficult to perform the alignment between the patterns of the object to be exposed and the openings of the photomask with high accuracy.